The present invention relates to a wheelchair conversion kit, and more particularly to a kit for converting a conventional wheelchair into an obstacle-mounting wheelchair capable of surmounting obstacles such as curbs.
Until relatively recently, wheelchairs were built in only a limited number of conventional designs and offered little choice to buyers with respect to maneouvrability, weight, and flexibility. The advent of sports, leisure, and recreational activities for wheelchair athletes and enthusiasts has created a demand for improvements in the conventional wheelchair designs, and wheelchairs geared to athletes are now made of lighter materials and composites, streamlined for maneouvrability, and have improved wheels and a greater number of adjustment features. One direction being pursued is to design wheelchairs that can more easily carry occupants over rough terrain and obstacles without undue challenge or difficulty. There have been several approaches taken in this regard.
One approach is disclosed in U.S. Pat. No. 5,308,098 (Brian J. Shea) which discloses a self-propelled all terrain wheelchair having a frame, a series of wheels mounted on each side of the frame, and a pair of continuous belts each mounted on a respective one of the sides of the frame so as to extend around one of the series of wheels. Spring-loaded handgrips, each positioned on a respective one of the belts, allow an occupant of the wheelchair to repetitively grasp and release the belts so as to propel the belts and thus the wheelchair forward. The wheels on the sides of the wheelchair are positioned such that each belt assumes the general shape of a parallepiped, with a front lower portion of each belt extending upwardly forwardly such that forward movement of the wheelchair allows obstacles such as sidewalk curbs to be overcome. A drawback of Shea""s construction, however, is that his wheelchair abruptly changes its orientation upon coming against an obstacle and again after having surmounted the obstacle, causing stress for an occupant if the wheelchair is moving forward with any speed. Shea""s belted construction does not include any means for absorbing shocks from impacting on an obstacle, and thus for smoothing an occupant""s ride over the obstacle.
U.S. Pat. No. 4,132,423 (John B. Chant) discloses an attachment that may be pivotably fitted to the forward end of the frame of a conventional wheelchair so as to allow the wheelchair to mount or dismount from obstacles in its path, such as sidewalk curbs. This arrangement suffers the same drawbacks as Shea in that a wheelchair occupant has to come to a stop at the obstacle before using the pivoting attachment. The curb-climbing wheelchair disclosed in U.S. Pat. No. 4,119,163 (Ball) has a tandem pair of rear axles, a pair of powered first wheels on one axle driving a pair of powered second wheels on the other axle. The one axle is mounted on a frame of the wheelchair, while the other axle is secured by link arms to the one axle to rotate around the one axle, allowing the wheelchair to climb over an obstacle. The climbing action of the wheelchair is not an integrated part of its normal forward motion; rather, the wheelchair must stop its forward motion at the obstacle to allow the pair of rear axles to be orientated to surmount the obstacle.
U.S. Pat. No. 4,119,163 (Ball) discloses a wheelchair capable of climbing a sidewalk curb. It has a liftable front wheel and a rotatable tandem rear wheel unit that are co-ordinated in a stepped procedure. This arrangement would not allow the wheelchair to simply glide over curbs and other obstacles, as is of greater importance to a lighter and more versatile wheelchair to the heavier motorized version shown in Ball.
The object of the wheelchair of the invention is to convert a conventional wheelchair into a wheelchair that is capable of surmounting obstacles such as curbs without any noticeable reduction in speed. This is accomplished by removing the large rear wheels and small forward wheels from the frame of the conventional wheelchair, and then pivotally suspending the frame from a pair of belted support members. A pair of obstacle-mounting guide members are then attached to a forward part of the wheelchair, either to a front end of the frame or to a forward position on the belted support members. The guide members are spring-biased to assume a normally upward and forward orientation on the wheelchair, but on impacting a curb or other obstacle a forward end of each guide member rotates upward and backward against the bias before reaching a point where the bias begins to rotate them back in the opposite direction. As the guide members rotate back, they lift the forward end of the wheelchair and thus the forward end of the belted support members, allowing the wheelchair to glide up and over the curb in a continuous steady motion.
The invention is a wheelchair conversion kit for converting into an obstacle-mounting wheelchair a conventional wheelchair having a frame, a main pair of circular wheels each mounted on a respective opposite side of the rear of the frame, and a steerable smaller pair of circular wheels each mounted on a respective opposite side of the frame forward of the main pair of circular wheels. Parts of the kit are adapted to be mounted to the frame after removal of the main pair of wheels and the smaller pair of circular wheels.
The parts in the kit include a pair of belted support members and a pair of obstacle mounting guide members. Each of the belted support members is adapted to be fitted to a respective side of the frame, and includes a frame structure on the periphery of which are mounted a series of load-bearing rotatable members, an endless belt mounted on the series of load-bearing rotatable members, and a pendulum member having one end pivotally mounted on the frame structure. The load-bearing rotatable members configure peripheral movement of the belt around the frame structure into a defined path, a first segment of the defined path being adapted to extend proximate to a surface of ground traversed by the obstacle-mounting wheelchair. The first segment has a shallow convex curvature such that only a portion of the first segment of the defined path of the belt is in contact with the ground at any one time. The pendulum member is adapted to extend downwardly in use from its one end, and has its other end adapted to be attached to the respective side of the lower frame. Each obstacle-mounting guide member has a first part adapted to be attached at a forward position on the wheelchair, and has a second part connected by a respective resilient member to the first part and biased so as to normally extend in an upwardly forwardly direction on the wheelchair.
When the obstacle-mounting wheelchair encounters obstacles of a defined size or less during forward movement, each second part of the guide members initially rotates to compress the respective resilient member after first contact with the obstacle. The resilient members then act to return the second parts toward their original positions, the action of the second parts in returning toward such original positions lifting a forward end of the first segment of the defined path of each belt and thereby allowing the obstacle-mounting wheelchair to smoothly mount the obstacle.
Each obstacle-mounting guide member may be adapted to be attached to the frame structure of a respective belted support member. Alternatively, each obstacle-mounting guide member may be adapted to be attached to a respective opposite side of the frame of the wheelchair. The obstacles of a defined size may be sidewalk curbs, steps, or thresholds.
The frame structure may be formed such that the periphery of the frame structure extends immediately adjacent the defined path of the endless belt. A first portion of the periphery of the frame structure extends immediately adjacent the first segment of the defined path of the endless belt. The periphery of the frame structure may have a series of rotary bearings rotatably secured thereto and extending in parallel, generally-equally-spaced relation therearound, the series of bearings extending between the endless belt and the periphery of the frame structure and allowing low-friction movement of the endless belt around the periphery of the frame structure. The periphery of the frame structure may have a generally triangular shape.
The second part of each guide member may include an arm normally extending upwardly forwardly on the wheelchair, first rotary member means mounted on one end of the arm, second rotary member means mounted on the other end of the arm, and an endless belt means extending around the first and second rotary member means. The endless belt means of each guide member is that part of the guide member that contacts the obstacle. The endless belt means rotates around the first and second rotary member means while maintaining contact with the obstacle as the second part of the guide member initially rotates to compress the respective resilient member and then returns toward its original position.
The one end of each pendulum member that is pivotally mounted on the frame structure of a respective belted support may have a series of holes extending therethrough. Each hole is adapted to receive a pivot pin that extends from the frame structure, each hole being incrementally angularly offset from each other such that a plane of the respective belted support member may assume a series of different lateral angles relative to the pendulum member.
A plate may be mounted between the one end of each pendulum member and the respective belted support member. The plate is mounted so as to remain both pivotally fixed on a pivot pin relative to the pendulum member and parallel to a plane of the belted support member. A range of relative pivotal movement between the pendulum member and the respective belted support member is determined by a pair of adjustably-positionable stops on the respective plate.